Britain's cities are overwhelmingly dependent on their European counterparts for trade, according to new research, underscoring the risk to jobs and growth in the U.K. post-Brexit.

An annual report from the Centre for Cities think tank found that the European Union (EU) is, by some distance, the biggest export market for almost every British city. The report also showed the U.K. would need to drastically increase trade to other international markets in order to offset a downturn in exports to the EU.

Currently, 46 percent of exports from U.K. cities are delivered to the EU which is three times more than to the US and 11 times more than to China, according to Centre for Cities' research.

"Securing the best possible EU trade deal will be critical for the prosperity of cities across Britain, and should be the Government's top priority as we prepare to leave the single market and potentially the customs union," Alexandra Jones, chief executive of Centre for Cities, said in a note.

"While it's right to be ambitious about increasing exports to countries such as the U.S. and China, the outcome of EU trade negotiations will have a much bigger impact on places and people up and down the country," she added.

The Centre for Cities report estimated that if exports to the EU decreased by 10 percent, as a consequence of Brexit, the country's urban areas would have to nearly double export trade to China or increase exports to the U.S. by almost a third to counterbalance the loss from the EU.

Businesses trade, not governments

The British Chamber of Commerce (BCC) published a survey on Monday which showed that business in Europe would continue to have a strong connection to European customers throughout Brexit negotiations and beyond.

The survey found 88 percent of U.K. firms surveyed were either committed to putting more resources into exporting with European partners or sticking with the same approach, in spite of Brexit uncertainty.

The survey of 1,500 small to medium sized business responded before U.K. Prime Minister Theresa May announced on January 17 that she would take the country out of the single market and attempt to negotiate a customs union deal with the bloc.

The government has since reaffirmed its commitment to beginning formal divorce talks with the EU by the end of March.

"These results are an important reminder of the fact that it is businesses that trade, not governments," Adam Marshall, BCC director general said.